1. Field of the Invention
This invention relates to hydraulic lift apparatus in general and to a hydraulically operated vehicular tailgate lift apparatus in particular.
2. Description of Related Art
Vehicular tailgate lift assemblies are used on a variety of products such as large trucks, loading vans, and, in particular, pick-up trucks. While these assemblies have been successful in general, their use is still problematic for a number of reasons. Many of the systems are quite complex, using a series of pulleys and cables to raise the tailgate, as in U.S. Pat. Nos. 4,813,842 and 3,887,092. The complexity of these systems can create problems with the maintainability and reliability of the system.
Other systems use hydraulic cylinders to raise the platform, as in U.S. Pat. No. 3,688,649; however, these systems require two cylinders, which must be coordinated to assure even lifting, or they rely on one cylinder which can create problems with the stability of the lift platform. This instability of the platform can limit the ability to place loads on one side or one corner of the platform for lifting. Systems using a centrally located cylinder can resolve lift imbalances, but require more space and expose many of the moving parts to the elements. This creates maintenance problems due to contamination as well as safety problems due to the exposed machinery.
Accordingly, it is an object of this invention to provide a tailgate lifting assembly that directly applies equal lifting forces to both sides of the lift platform simultaneously.
Another object of this invention is to reduce the complexity and cost typically associated with tailgate lift assemblies.
Yet another object of the invention is to provide a tailgate lift assembly that is easy to use and to maintain.
A further object of this invention is to provide tailgate lift assembly that is compact and unobtrusive.
Another object of this invention is to provide a tailgate lift assembly where the lift mechanism is not exposed to the environment.
These and other objects of the invention are achieved in a vehicular tailgate lift assembly in accordance with the invention.